I haven't really noticed the difference between either of the grips when playing the game. What does each one do to effect the weapon?
According to this forum post the:
Vertical does horz/vert recoil in a larger percentage then the angled but the angled lets you ADS faster while still giving small vert/horizontal recoil reduction.
This information seems to have come from one of the dev streams(Twitch link seems to be dead) and looks to be confirmed by additional forum members. Not sure how exactly accurate it is though.